The blaze destroyed the building at 300 Front Ave., and it collapsed while firefighters tried to put out the flames. Fire Investigator Pablo Martinez called the fire suspicious because firefighters found the back door open, and footprints in the snow.

He had not determined the cause. It could have been a homeless person trying to stay warm, somebody stealing copper, or someone purposely setting it on fire, officials speculated. Firefighters worked several hours to bring the fire under control, then sprayed water on the smoldering rubble throughout the day.

The fire started in back, where firefighters found the open door. A passer-by reported the blaze at 2:19 a.m., and firefighters two minutes later reported the back of the structure engulfed in flames. Smoke covered a wide area near the Grand River, U.S. 131 and parts of downtown.